What is Lumbosacral Plexopathy?
The lumbosacral (LS) plexus, which is a network of nerves in the lower back and pelvic region, can sometimes get injured. This condition is known as LS plexopathy, and while it’s not entirely uncommon, it can be somewhat tricky to identify and manage. It’s less frequent than a similar issue known as brachial plexopathy. People with LS plexopathy usually report low back and/or leg pain. Some can also have muscle weakness, numbness, tingling sensations or issues with their natural body functions such as bladder control.
Various factors can cause LS plexopathy. Some of the main ones include diabetes, traumatic injury, growth of abnormal tissues (neoplasms), and pregnancy. The treatment options for this condition differ a lot and mostly depend on what specifically is causing the issue in the first place.
It’s important to take note that LS plexopathy can significantly degrade a person’s quality of life. Thus, it’s crucial to identify and manage this condition as early as possible to reduce complications and the risk of death.
What Causes Lumbosacral Plexopathy?
Understanding the anatomy of our body is crucial for understanding LS plexopathy, a nerve disorder. The LS plexus is a network of nerves that connects the lower spine to the legs. It’s formed by the nerves from the first to fourth lumbar and sacral part of your spine, and a little contribution from the twelfth thoracic nerve. The lumbar part is above, and the sacral part of the plexus is below the pelvic area.
Part of the LS plexus, the lumbar plexus, has nerves that pass through the muscle of the lower back and split into two branches. These nerves further divide to form several individual nerves. For instance, the femoral nerve, important for leg movement, is formed from certain branches. Other nerves originating from the lumbar plexus include the iliohypogastric nerve, ilioinguinal nerve, genitofemoral nerve, and the nerve on the side of the thigh. Another key nerve, the sciatic nerve, consists of branches from the lumbosacral trunk, and first and second sacral nerve.
Another part of the LS plexus, the sacral plexus, consists of several important nerves related to hip and leg movement. Blood to these nerves comes from the lumbar arteries branching from the main abdominal artery. Additional blood supply comes from arteries in the abdomen and hip regions.
The LS plexus’s location near the abdomen and pelvis makes it susceptible to various injuries and conditions. These include:
1. Direct trauma, such as from dislocation of the hip, fractures in the sacral spine, or complications from anesthetic procedures.
2. Metabolic, inflammatory, and autoimmune conditions like type 2 diabetes, amyloidosis, and sarcoidosis – a disease that causes inflammation in the body.
3. Infections such as osteomyelitis – infection of the bone, chronic infections like tuberculosis, fungal infections, and other infections like Lyme disease, HIV/AIDS, and Herpes zoster (shingles).
4. Abscesses – collection of pus, in the psoas muscle.
Other potential causes include radiation therapy for abdominal and pelvic cancers, conditions related to pregnancy particularly in the last stage or after delivery, and complications from pelvic surgeries. In some cases, damage to the blood vessels supplying the LS plexus, due to procedures like femoral vessel catheterization or compression from blood clots, aortic dissection, etc., can also contribute to this nerve disorder.
Risk Factors and Frequency for Lumbosacral Plexopathy
Several different factors can cause LS plexopathy, so the average age of diagnosis and how common it is can vary. On average, it is diagnosed around the age of 65. It is more common in women, as pregnant women and women with gynecological cancers are more at risk.
Diabetic amyotrophy affects about 4.2 people out of 100,000 each year, and happens in 0.8% of people with diabetes. On average, those with diabetic amyotrophy have had diabetes for around four years and have a hemoglobin A1c level of 7.5% when diagnosed.
- When LS plexopathy is caused by tumors, it’s often found in the L4-S1 segment of the spine (over 50% of cases), followed by the L1-L4 segment (31%) and throughout the whole spine (about 10%).
- In 73% of cases, LS plexopathy is present because a tumor in the abdomen or pelvis is pressing against or has spread into the nerves.
- LS plexopathy shows up within a year of diagnosis in over a third of people with primary tumors.
- In 15% of cases, having LS plexopathy leads to the diagnosis of cancer.
About 0.7% of LS plexopathy cases happen after a significant pelvic injury. This increases to 2% after a severe sacral (lower part of the spine) injury.
LS plexopathy happens in about 1 in every 2000 to 6400 births.
Retroperitoneal hematoma (bleeding into the area behind the abdominal cavity) after a femoral artery catheter is quite rare (0.5% of cases). Of these, 20% have damaged femoral nerves, and 9% develop LS plexopathy.
Signs and Symptoms of Lumbosacral Plexopathy
Lumbar Sacral (LS) plexopathy diagnosis relies heavily on a detailed medical history and physical exam. The patient usually has lower back pain that spreads to one side and can be influenced by position, worsening when laying flat. In cases where diabetes is the underlying cause, the main complaint is generally a one-sided pain in the upper part of the thigh. This pain can come with numbness, tingling, or abnormal sensations in the legs, typically affecting only one side. If radiation therapy is the cause, the plexopathy usually does not cause pain.
The time frame for these symptoms can range from very short (such as after a car accident) to very long (like after radiation therapy). In more serious cases, muscle weakness and shrinking can happen. Bladder or bowel control issues are uncommon, but if they occur they could indicate a condition called cauda equina syndrome. Other symptoms like fever, chills, night sweats, fatigue, and weight loss may imply cancer or an infection. Additionally, a patient’s history of specific conditions or events like car accidents, abdominal or pelvic tumors, radiation therapy, abdominal surgery, diabetes, bleeding disorders, or recent pregnancy can help pinpoint LS plexopathy as the cause and provide clues to its origin.
In mild cases, physical examinations might not show anything unusual. However, for injuries, there might be visible bruises. The straight-leg-raising test could come out positive in more than half of patients. Doctors might also notice an uneven weakness of the lower limb muscles alongside an unbalanced absence or decrease of deep tendon reflexes. Because of the involvement of the lumbar plexus, reflexes in the knee are affected in lumbar plexopathy while ankle reflexes are impacted in sacral plexopathy. Sensory loss might be noticeable following a pattern that corresponds to certain nerves or nerve roots. Sensory changes to certain areas of the leg, foot, and perineum can suggest an involvement of either the lumbar or the sacral plexus. Additionally, the spine may be tender, particularly in cases related to sacral fracture or infection. Doctors should perform a rectal exam to assess rectal tone and check the groin area for possible hematomas. Symptoms like saddle anesthesia (loss of sense in the inner thighs, back of the legs, and rectal area) and problems with bowel or bladder control are rare, but they can complicate the differentiation from other conditions such as cauda equina or conus medullaris syndromes.
Testing for Lumbosacral Plexopathy
When diagnosing LS plexopathy, a condition that affects the nerves in your lower spine, tests such as a magnetic resonance imaging (MRI) scan and electrodiagnostic studies are usually required. These help your doctor to confirm a diagnosis.
An MRI scan uses magnetic fields and radio waves to create detailed images of the body. MRIs taken with a substance called gadolinium contrast are considered the best imaging test to check the LS plexus, the network of nerves in the lower spine area. If you have certain health conditions, such as a pacemaker that is not compatible with MRI machines, a computed tomography (CT) scan – a type of X-ray that provides detailed images – may be used instead. Some doctors find MR neurography, a more specialized type of MRI, helpful for pinpointing the cause of leg pain due to nerve damage in your spine.
If cancer is suspected, additional imaging such as a positron emission tomography (PET) scan may be necessary. PET scans can provide information on the extent of cancer, its stage, and help in planning treatment.
Electromyography (EMG) is a diagnostic test that measures the electrical activity of muscles. It can help differentiate LS plexopathy from other nerve or spine conditions. It’s also useful in locating where the nerve injury is and for distinguishing between cancer-related and radiation-induced plexopathy. Magnetic root stimulation is another diagnostic method that can be used when someone can’t have an EMG due to other health conditions such as bleeding disorders.
Various blood tests can assist in identifying the cause of LS plexopathy. Standard tests include a complete blood count to check the different types of cells in your blood, inflammation markers like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and tests for autoantibodies, proteins your immune system makes that attack your own cells and tissues. Additional tests may be conducted based on your symptoms or medical history.
If the cause of LS plexopathy cannot be identified with these methods, a lumbar puncture or nerve biopsy might be carried out. In case of suspected cancer, a biopsy or sample of tissue from pelvic organs or the affected nerve root might be required to confirm the diagnosis.
Treatment Options for Lumbosacral Plexopathy
Treatment for lumbosacral plexopathy, a condition affecting the nerves in the lower back and pelvis, depends on what’s causing the condition. For general symptoms management, medications that reduce pain (analgesics) and help relax the muscles (muscle relaxants) are given. This may include over-the-counter anti-inflammatory drugs, or prescription medications like pregabalin, gabapentin, duloxetine, amitriptyline, and even opioids for severe pain. If the patient has difficulty lifting their foot (foot drop), ankle-foot braces can be used. Antibiotics and antifungal medications are used if the cause is an infection.
Diabetic amyotrophy is a nerve disorder that can cause muscle weakness and pain in the hips, thighs, and legs. It’s usually a temporary condition that gets better with good blood sugar control. However, treatments for nerve pain may also be recommended. In severe cases that don’t respond to other treatments, steroids, intravenous immunoglobulin (a type of blood product), cyclophosphamide (a drug that modulates the immune system), and plasma exchange (a process that filters the blood) might be used.
If the cause of the lumbosacral plexopathy is a tumor, then treating the primary tumor would be the priority. For severe pain, a medical procedure known as a dorsal rhizotomy could be considered. This involves cutting specific nerve roots to reduce pain and reliance on opioid painkillers, and is usually considered for patients in the late stages of their illness.
Radiation plexopathy is nerve damage caused by radiation therapy. It may not cause pain, but instead can cause weakness and changes in sensation. It can affect both sides of the body and may occur years after radiation. Unfortunately, there’s no specific treatment for it. Physiotherapy and rehabilitation are the main forms of treatment. Further radiation treatment is usually avoided.
Surgery can also be a treatment option in certain cases. For patients who experienced nerve damage due to pelvic fractures, surgical nerve repair techniques and nerve grafting (transplanting nerve tissue) have shown to improve muscle function.
In the case of a retroperitoneal hematoma, a buildup of blood in the space behind the abdominal cavity, treatment is usually non-surgical. This involves blood transfusions and rest. However, if the hematoma gets worse or if the patient’s neurological function declines, surgery might be recommended.
What else can Lumbosacral Plexopathy be?
Various medical conditions can cause similar symptoms, such as:
- Cauda equina syndrome: A rare disorder that affects the bundle of nerve roots at the lower end of the spinal cord
- Conus medullaris syndrome: A condition that causes weakness of the legs and bowel or bladder dysfunction
- Hereditary sensory and motor neuropathy (also called Charcot-Marie-Tooth disease): A group of disorders that damage the peripheral nerves
- Lumbosacral radiculopathy: Irritation or compression of one or more nerve roots in the lower part of the spine
- Mononeuropathies like Femoral neuropathy, sciatic neuropathy, common femoral neuropathy: These are conditions where a single nerve or nerve group is damaged
- Polyneuropathy, for instance, diabetic neuropathy, chronic inflammatory demyelinating neuropathy (CIDP), drug-related neuropathy: These are conditions affecting multiple peripheral nerves
- Spinal canal stenosis: A narrowing of the spaces within your spine
- Spinal cord tumors: Abnormal growths developing within or near the spinal cord
What to expect with Lumbosacral Plexopathy
The outlook for a patient with a medical condition called LS plexopathy depends on several factors. These include the specific cause of the condition, how well it responds to treatment, and when treatment begins. A good prognosis is likely for patients whose LS plexopathy is due to pregnancy, a condition known as retroperitoneal hematoma, or diabetes-related muscle weakness.
Most patients whose LS plexopathy is caused by pregnancy find that their symptoms completely go away in two to six months after giving birth. On the other hand, if the LS plexopathy is caused by cancer, the condition often gets worse over time. The outlook in such cases is generally poor, with patients living on average six months after diagnosis. However, lymphoma, a type of cancer, was found to respond best to treatment in these cases.
At a follow-up examination 42 months after diagnosis, it was found that 86% of patients with LS plexopathy caused by cancer had unfortunately passed away. In cases where the LS plexopathy is caused by an injury, the prognosis is generally unfavorable. But in a study of 72 patients with injury-caused LS plexopathy, more than two-thirds, or about 70% of them, recovered on their own within 18 months.
Possible Complications When Diagnosed with Lumbosacral Plexopathy
Common issues include:
- Deteriorating neurological condition
- Persistent severe pain
- Constant bedsores
- Frequent infections
- Stiff, immovable joints
Preventing Lumbosacral Plexopathy
The patient should be made aware about the specifics of their condition and the root cause. As mentioned before, LS plexopathy due to pregnancy, retroperitoneal hematoma (a solid swelling of clotted blood within the tissues in the back of the abdomen), and diabetic amyotrophy (a nerve disorder related to diabetes that affects the muscles in the hips, thighs and legs) usually come and go and tend to get better naturally over time. Patients diagnosed with cancer should be given guidance on what to expect next and be provided with a comprehensive plan for further diagnosis and treatment. Symptoms might gradually worsen over time, requiring the patient to need help with walking and everyday tasks.
